The code should be written such a way that it uses the best practices, easy to extend in the future, and maintainable.

A. This can be done a number of ways. The following code snippets take following key aspects into consideration.

1. Use generics.

2. Code to interface.

3. Make it extendable. New predicate implementation classes can be easily added in the future like OddNumberPrdeicate, PrimeNumberPredicate, etc and no change is required to the FilteredList class. It just takes a source list and a predicate implementation as arguments to create a sublist. If you need to build
heirachy of sublists, you can add a parent field in FilteredList class to maintain a hierachy.

4. Easy to test. The JUnit test classes are provided to test the FilteredList and the Predicate classes. Both happy path and exceptional paths are tested.

5. Composition is favored over inheritance hence the FilteredList was not defined as public class FilteredList extends List, instead the sublists was composed within FilteredList.

Here is the sample code.

Step 1: Define the Predicate interface

public interface Predicate<E> {
boolean evaluate(E object);
}

Step 2: Define the implementation classes for the Predicate interface. One for filtering even numbers and another one for filtering factors of five.